System For Regulating A Load Voltage In Power Distribution Circuits And Method For Regulating A Load Voltage In Power Distribution Circuits

ABSTRACT

The present invention refers to a system for regulating a load voltage (C) in power distribution circuits comprising at least: a regulation transformer ( 2 ) the secondary winding of the regulatory transformer ( 2 ) being operatively arranged in series between a power source (F) and the load (C), the power source (F) being capable of providing a supply voltage (VAL) to the load (C); a measuring device ( 5 ) operatively associated to the load (C), the measuring device ( 5 ) being capable of measuring at least one value of an electric signal of the load (SCA); a control device ( 4 ) operatively associated to the measuring device ( 5 ), the control device ( 4 ) being capable of comparing the value of the electric signal of the load (SCA) with a pre-established reference value and providing a correcting electric signal (SCO); and an actuation device ( 3 ) operatively associated to the control device ( 4 ), wherein the actuation device ( 3 ) is capable of providing an adjustment voltage (VAJ) proportional to the correcting electric signal (SCO), the adjustment voltage (VAJ) being applicable to fixed electric taps of the primary winding of the regulation transformer ( 2 ), the fixed electric taps being configured to remain immovable when there is a variation of the adjustment voltage (VAJ), the regulation transformer ( 2 ) being capable of transforming the adjustment voltage (VAJ) into a regulation voltage (VRE), the regulation voltage (VRE) being added in module and phase to the supply voltage (VAL). The present invention also refers to a method executed by the above-mentioned system.

The present invention refers to a system for regulating a load voltagein power distribution circuits. More particularly, the invention refersto a system capable of automatically adjusting a voltage supplied by apower distribution circuit to at least one load, increasing ordecreasing its value, pursuant to variations in measurements of electricsignals of said load.

The present invention also refers to a method for regulating the loadvoltage in power transmission and distribution circuits.

DESCRIPTION OF THE STATE OF THE ART

In electric power transmission and distribution circuits, it isessential that the voltage supplied to the user be kept constant so asto avoid disruptions such as, for example, mal functioning and damage toindustrial equipment, household appliances, electronic and computingitems. Accordingly, equipments are used that enable the voltage to beincreased or decreased, as the demand so requires. Due to variousfactors such as, for example, alterations in load, voltage regulatorsand/or transformers are used, associated to switchers under load capableof altering the voltage automatically, without interrupting the supplyof power to the user.

The voltage regulator basically comprises a transformer having a windingprovided with shunts or taps, with a certain turn ratio, linked to amechanical switch under load. Normally, the mechanical switch is mountedinside a tank comprised by the transformer, submersed in insulating oil(mineral oil). In this sense, the tank should have its volume oversizeddue to the need to install the switch in its inner portion, which alsomeans an increased volume of insulating liquid.

Some types of voltage regulators also comprise a reactor linked to theswitch contacts to limit the electric current and provide anintermediary voltage between two positions of said taps.

Generally, the connection position of the taps to a mechanical switch isautomatically shifted by a control system, which measures the loadcurrent from an electronic panel and commands the drive of the switch,from the voltage of the load. Switching to a tap defined by the controlsystem is done mechanically by the displacement of the movable contactsthat slide over the surface of the fixed contacts deployed in a circle,avoiding the interruption of the current energizing. Said displacementbetween taps requires an electric motor and other mechanical parts, suchas gearwork, supports, among others, and each change of tap creates anelectric arc between the movable contact and the fixed contact.

Said electric arc removes metal particles from the contacts, causing itswear and contributing to the formation of inflammable gases whichcontaminate the insulating oil, decreasing its insulation feature andeven causing the risk of explosion under certain conditions.

Additionally, there are voltage regulators capable of altering thedirection of the current circulation in the taps, whereby altering itspolarity, enabling that this setting increase or decrease the voltagerequired according to the position of the taps, wherein each tapcorresponds to a certain turn ratio, thus being added or subtractedaccording to the polarity of the switch.

However, since the switch is mechanical and is rotated over the windingsof the transformer, there is the drawback of needing to limit theadjustment of the output voltage to a fixed and limited number ofpositions of the switch, in addition to generating electric arcs uponeach change of position, as already mentioned previously.

Accordingly, the switchers are submitted to constant wear, requiringperiodic maintenance for cleaning and even replacement, demandingtransport of the regulators to a suitable site, involving undesirableexpenses and disruptions. This transport contributes to the increase inrisk of leakage of the insulating oil in a potential accident situation,jeopardizing the environment and people. Additionally, the transportrequires expenditures with human resources, appliances, vehicles, fuel,and other items. These expenses are passed onto the consumers throughadditional taxes.

Such dangerous situations, as well as the high expenditures involvedwith frequent maintenance of the voltage regulator, could be decreasedand/or avoided if the mechanical switch were substituted for a systemthat increased or decreased the output voltage, without generatingelectric arcs and without using insulating oil.

Some of the problems mentioned above are detected in the followingsolutions, known in the state of the art, presented below.

Brazilian Patent Document PI 0110005-0 describes a switching transformerconnected to the input terminals of a voltage source V_(E) to beregulated. Said transformer presents a variable turn ratio k so as togenerate a voltage kV_(E) in its secondary. This turn ratio iscontrolled by control and command devices based on the output voltageV_(s) of the voltage adapter. The voltage kV_(E) is fed to a secondtransformer having a fixed turn ratio k′, connected in series to thevoltage adapter output. The transformer generates a voltage k′kV_(E) inits secondary which is added to the voltage V_(s) of the adapter. Thisarrangement is only applicable for a low voltage network, in addition tocomprising mechanical switchs that have the drawback of limiting theregulation of the output voltage to a fixed number of activated switchs,and electric arcs are still generated upon each change of actuation.

British document UK 2324389 describes a transformer which secondary isconnected in series to a controlled voltage line, to add or subtractvoltage to or from the line. The primary of this transformer is coupledto a switching network formed by a transformer having a variable turnratio, which is controlled by a loop comprising a microprocessor and 4relay. This arrangement also comprises closed relay contacts, limitingthe shifting of the output voltage to a fixed number of activatedcontacts, besides generating electric arcs upon each change ofactuation.

Accordingly, the documents of the state of the art do not describe afull and satisfactory solution to solve all the existing problems,besides presenting apparently high implementation and maintenance costs.

OBJECTIVES OF THE INVENTION

A first objective of the present invention consists of providing asystem capable of automatically regulating an electric voltage suppliedto a load comprised by an electric power distribution circuit, withoutthe need to interrupt the supply of electric power to the load, soreducing and simplifying maintenance and the replacements required bysystems known in the state of the art, further reducing the costs andrisks to the environment and to people.

A second objective of the present invention consists of providing amethod for automatically regulating an electric voltage supplied to acharge comprised by an electric power distribution circuit.

BRIEF DESCRIPTION OF THE INVENTION

The first objective of the present invention is achieved through theprovision of a system for regulating a load voltage in powerdistribution circuits comprising at least: a regulation transformerhaving a primary winding and a secondary winding, the secondary windingof the regulation transformer being operatively arranged in seriesbetween the power source and the load, the power source being capable ofproviding a supply voltage to the load; a measuring device operativelyassociated to the load, the measuring device being capable of measuringat least one value of an electric signal of the load; a control deviceoperatively associated to the measuring device, the control device beingcapable of comparing the value of the electric signal of the load with apre-established reference value and providing a correcting electricsignal; and an actuation device operatively associated to the controldevice, wherein the actuation device is capable of providing anadjustment voltage proportional to the correcting electric signal, theadjustment voltage being applicable to fixed electric taps of theprimary winding of the regulation transformer, the fixed electric tapsbeing configured to remain immovable when there is a variation of theadjustment voltage, the regulation transformer being capable oftransforming the adjustment voltage applied to the primary winding intoa regulation voltage to be applied to the secondary winding, theregulation voltage being added in module and phase to the supplyvoltage.

The second objective of the present invention is achieved through theprovision of a method that comprises the steps of: i) supplying a supplyvoltage to the load; ii) measuring at least one value of an electricsignal of the load; iii) comparison between at least one value of theelectric signal of the load obtained in step ii with a pre-establishedreference value; iv) calculating and providing a correcting electricsignal; v) providing an adjustment voltage from the correcting electricsignal obtained in step iv; vi) transforming the adjustment voltageobtained in step v into a regulation voltage; vii) adding in module andphase of the regulation voltage obtained in step iv with the supplyvoltage; and viii) supplying the sum of voltages obtained in step viifor the load.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described in greater detail, withreference to the appended drawings, wherein:

FIG. 1—represents a schematic block diagram of a system for regulating aload voltage in power distribution circuits, the object of the presentinvention; and

FIG. 2—represents a flowchart of a method for regulating load voltage inpower distribution circuits.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic block diagram of a system for regulatinga load C voltage in power distribution circuits, according to apreferred embodiment of the present invention.

The power distribution circuit preferably consists of a circuit capableof providing electric power to loads C such as, for example, residences,households, buildings, condominiums, factories, industrial plants, aswell as power stations and sub-stations. Therefore, the system forregulating the present invention is applicable preferably in highvoltage circuits such as, for example, in the order of 13800 V, 24200 Vor 34500 V. Optionally, the system can also be applied to average and/orlow voltage circuits.

As can be seen in FIG. 1, said system comprises at least a power sourceF capable of providing a supply voltage VAL to the load C.

The load C is associated to a regulation transformer 2 having a primarywinding and a secondary winding operatively arranged in series betweenthe power source F and the load C.

The load C is also operatively associated to a measuring device capableof measuring at least one value of an electric signal of the load SCA.

The measuring device 5 preferably but not obligatorily consists of amultimeter capable of measuring the voltage signal of the load and/or acurrent signal of the load.

The voltage measuring device 5 is operatively associated to a controldevice 4 capable of comparing the value of the electric signal of theload SCA with a pre-established reference value. This reference valueconsists of a value considered excellent, proportional to an idealvoltage value which is desirable to supply to the load C.

The control device 4 is also capable of providing a correcting electricsignal SCO which can be a voltage or electric current, depending on theform of implementing the system.

Preferably, the control device 4 comprises at least a microprocessor ora microcontroller capable of running a computer program that allows theprovision of the correcting electric signal SCO. The correcting electricsignal SCO consists of a digital and/or analog electric signal that canbe provided directly by an output pin of the microprocessor ormicrocontroller, or can be provided by a filter (circuit or electriccomponent) associated to said output pin. The computer program can bestored in an external memory associated to the microprocessor ormicrocontroller or stored in an internal memory of the microprocessor ormicrocontroller.

Accordingly, the comparison, calculation and provision of the correctingelectric signal SCO are carried out by a control algorithm contained inthe computer program.

Additionally, it is also possible to establish a permitted tolerancevalue (error), wherein the control device 4 is configured to provide thecorrecting electric signal SCO only when there is extrapolation of thevalue of the electric signal of the load SCA beyond the limitsdetermined by this tolerance. Optionally, the control device 4 can beconfigured to provide the correcting electric signal SCO constantly,regardless of the magnitude of the difference between the value of theelectric signal of the load SCA and the pre-established reference value.Further, other parameters can be included, if necessary.

Evidently, both the pre-established reference value and the tolerancevalue can be adjusted and altered pursuant to the application,convenience and needs.

The control device 4 also comprises an interface panel for interactionwith an operator. The interface panel has visualization means (e.g. LCDdisplay) and command buttons/keys.

Alternatively, the control device 4 can be implemented integrally byanalog electronic components and/or integrated circuits (chips)operatively associated amongst themselves, so as to dispense with theuse of a microprocessor or microcontroller.

The control device 4 is operatively associated to an actuation device 3capable of providing an adjustment voltage VAJ, proportional to thecorrecting electric signal SCO, to the regulation transformer 2. Moreparticularly, an adjustment voltage VAJ is applicable to fixed electrictaps of the primary winding of the regulation transformer 2. Thisadjustment voltage VAJ is transformed by the regulation transformer 2into a regulation voltage VRE to be applied to its secondary winding.

Bearing in mind that the secondary winding of the regulation transformeris associated in series between the power source F and the load C, theregulation voltage VRE is added in module and phase to the supplyvoltage VAL, so as to correct or adjust the voltage provided to the loadC, according to the demands and variations presented by the powerdistribution circuit. Therefore, the fixed electric taps remainimmovable when there is a variation in the adjustment voltage VAJ. Thecorrection (adjustment) of the voltage provided to the load C isperformed entirely electronically, without involving any kind ofmovement of mechanical parts.

Therefore, contrary to systems known in the state of the art, the systemof the present invention does not use movable mechanical contacts thatgenerate electric arcs capable of accelerating wear and requiringfrequent maintenance.

Besides, the system of the present invention dispenses with the use ofinsulating oil, eliminating the risk of contaminating the environment,fire and explosion upon implementation, maintenance and transport as maybe necessary.

Additionally, the system of the present invention dispenses with the useof an electric motor and other mechanical parts, such as gearwork,supports, among others, which simplifies and reduces the final costsinvolved in its implementation and maintenance.

Furthermore, the variation of the regulation voltage VRE is performed ona continual basis, without steps of voltage, whereby permitting finervoltage adjustments with greater precision, optimizing the performanceof the equipments and economizing power.

It is also important to note that the operations of measuring,comparing, correcting/adjusting, transforming, adding and strengtheningof the corrected voltage to the load C is performed automatically by thesystem, according to the measurement variations of the voltage orcurrent of the load C, without any kind of power interruption.

The actuation device 3 comprises at least one power circuit capable ofhandling the correcting electric signal SCO to provide the adjustmentvoltage VAJ. As already described previously, the value of theadjustment voltage VAJ is proportional to the value of the correctingelectric signal SCO.

The internal power circuit has, for example, at least one AC/DCconverter and/or one DC/AC converter and/or amplifying circuits. TheAC/DC, DC/AC converters and the amplifying circuits are widely known inthe state of the art and will not be discussed herein.

Therefore, the specification configuration of the actuation device 3 mayvary according to the convenience and needs of use, and it is irrelevantto define the scope of protection of the invention.

The actuation device 3 is electrically powered by an auxiliarytransformer 1, as can be seen in FIG. 1. This way, the auxiliarytransformer 1, operatively arranged between the power source F and theactuation device 3, is capable of providing an auxiliary voltage VAU tothe actuation device 3.

The auxiliary transformer 1 preferably consists of a power transformer.Said transformer has a high voltage (primary winding) side associated tothe power source F and a low voltage side associated to the actuationdevice 3.

Thus, it is possible to reduce the risk of accidents when accessingand/or performing maintenance on the actuation device 3, control device4 and on the regulation transformer 2, as the entire control forproviding the regulation voltage VRE is carried out on the low voltageside.

FIG. 2 illustrates a flowchart of the steps performed by the system ofthe present invention. These steps form/compose a method for regulatingthe voltage of the load C in power distribution circuits.

Said method comprises the steps of:

-   -   i) supplying a supply voltage VAL to the load C;    -   ii) measuring at least one value of an electric signal of the        load SCA;    -   iii) comparison between at least one value of the electric        signal of the load SCA obtained in step ii with a        pre-established reference value;    -   iv) calculating and providing a correcting electric signal SCO,        preferably, if the result of the comparison of step iii is not        comprised by the pre-established tolerance range;    -   v) providing an adjustment voltage VAJ from the correcting        electric signal SCO obtained in step iv;    -   vi) transforming the adjustment voltage VAJ obtained in step v        into a regulation voltage VRE;    -   vii) adding the regulation voltage VRE obtained in step iv with        the supply voltage VAL in module and phase; and    -   viii) supplying the sum of voltages obtained in step vii for        load C.

In step iii described above, it is possible to make a comparison, forexample, by calculating the difference in module and phase between theelectric signal of the load SCA and the pre-established reference value.

Having described an example of a preferred embodiment, it should beunderstood that the scope of the present invention encompasses otherpotential variations, and is limited only by the content of the appendedclaims, possible equivalents being included therein.

1. System for regulating a load (C) voltage in power distributioncircuits comprising at least: a regulation transformer (2) having aprimary winding and a secondary winding, the secondary winding of theregulation transformer (2) being operatively arranged in series betweena power source (F) and the load (C), the power source (F) being capableof providing a supply voltage (VAL) to the load (C); a measuring device(5) operatively associated to the load (C), the measuring device (5)being capable of measuring at least one value of an electric signal ofthe load (SCA); a control device (4) operatively associated to themeasuring device (5), the control device (4) being capable of comparingthe value of the electric signal of the load (SCA) with apre-established reference value and providing a correcting electricsignal (SCO); and an actuation device (3) operatively associated to thecontrol device (4), the actuation device (3) being capable of providingan adjustment voltage (VAJ) proportional to the correcting electricsignal (SCO), the system being characterized in that the adjustmentvoltage (VAJ) is applicable to fixed electric taps of the primarywinding of the regulation transformer (2), the fixed electric taps beingconfigured to remain immovable when there is a variation of theadjustment voltage (VAJ), the regulation transformer (2) being capableof transforming the adjustment voltage (VAJ) applied to the primarywinding into a regulation voltage (VRE) to be applied to the secondarywinding, the regulation voltage (VRE) being added in module and phase tothe supply voltage (VAL).
 2. System according to claim 1, characterizedby the actuation device (3) comprising at least an internal powercircuit capable of handling the correcting electric signal (SCO) toprovide the adjustment voltage (VAJ).
 3. System according to claim 2,characterized by the internal power circuit having at least an AC/DCconverter and/or a DC/AC converter.
 4. System according to claim 1,characterized by comprising an auxiliary transformer (1) operativelyarranged between the power source (F) and the actuation device (3), theauxiliary transformer (1) being capable of providing an auxiliaryvoltage (VAU) to the actuation device (3).
 5. System according to claim1, characterized by the measuring device (5) consisting of a multimetercapable of measuring a voltage signal and/or current signal of the load.6. System according to claim 1, characterized by the control device (4)comprising at least a microprocessor or a microcontroller capable ofrunning a computer program that allows the provision of the correctingelectric signal (SCO) to the actuator device (3).
 7. Method forregulating a load (C) voltage in power distribution circuits,characterized by comprising the steps of: i) supplying a supply voltage(VAL) to the load (C); ii) measuring at least one value of an electricsignal of the load (SCA); iii) comparison between at least one value ofthe electric signal of the load (SCA) obtained in step ii with apre-established reference value; iv) calculating and providing acorrecting electric signal (SCO); v) providing an adjustment voltage(VAJ) from the correcting electric signal (SCO) obtained in step iv; vi)transforming the adjustment voltage (VAJ) obtained in step v into aregulation voltage (VRE); vii) adding the regulation voltage (VRE)obtained in step iv with the supply voltage (VAL) in module and phase;and viii) supplying the sum of voltages obtained in step vii to the load(C).
 8. Method according to claim 7, characterized by the fact that instep iii the difference in module and phase between the electric signalof the load (SCA) and the reference value is calculated.